const myArr = [1, 2, 3]
myArr.foo = 'baz'//相当于添加了一个类似length的属性
myArr.push('test')
console.log(myArr);
console.log(myArr.foo);
console.log(myArr.length);
myArr['name']='window'//相当于添加了一个类似length的属性
console.log(myArr);
console.log(myArr.name);
console.log(myArr.length);
myArr['3']='happy'
console.log(myArr);
console.log(myArr[3]);
console.log(myArr.length);
